This document discusses abrasives used in dentistry. It defines abrasion and describes the different types including two-body, three-body, and erosion abrasion. The principles of cutting, grinding, and polishing are explained. Desirable characteristics of abrasives and factors affecting abrasion rates are outlined. Various natural and synthetic abrasives are classified and their uses described, including diamond, aluminum oxide, silicon carbide, and others. Recent advances in abrasives like air abrasion technology and CVD diamond coated burs are also mentioned.

1. Abrasives
Presented By : Arpit Viradiya Guided By : Dr Sandeep Metgud
Dr Deepali Agrawal

2. Contents
• Definition
• Abrasive action
• Types of abrasion
• Principles : Cutting Grinding & Polishing
• Desirable Characteristics Of An Abrasive
• Factors affecting rate of abrasion
• Abrasive instrument design
• Classification of abrasive agents
• Precautions
• Biological hazards of abrasive agents
• Recent Advances
• Summary & Conclusion

3. • Craig has defined abrasion as:
• "A process of wear whereby a hard rough
surface (like a sand paper disk) or hard
irregular shaped practicles (like those in an
abrasive slurry) plough grooves in a softer
material and cause materials from these
grooves to be removed from the surface".

4. Abrasive action
Harder material comes into frictional contact with
the substrate
Contact generates tensile and shear stresses
Break atomic bonds
Substrate particles are removed

5. Types of abrasion
1. Two-body abrasion
• Abrasive bonded to instrument
Eg - diamond bur abrading a tooth.

6. Three-body abrasion
• Non bonded abrasives
• Abrasive particles are free
Eg - dental prophylaxis paste

7. Erosion
• Wear caused by hard particles impacting a
substrate surface, carried by a stream of
liquid or stream of air. Eg. Sand blasting a
surface
• Chemical erosion
Acid etching
Enhance bonding

8. Principles
Cutting
• Use of any instrument in a bladelike fashion
• Regularly arranged blades that remove small
shavings of the substrate
• Unidirectional cutting pattern

9. Grinding
• Removes small particles of a substrate
through the action of bonded or coated
abrasive instruments
• Predominantly unidirectional
• Innumerable unidirectional scratches
• Eg: a diamond coated rotary instrument

10. Polishing
• Most refined of the finishing processes
• Multidirectional in its course of action
• Acts on an extremely thin region of the substrate
surface
• Progress - fine polishing media
• Final stage produces fine scratches - not visible
unless greatly magnified

11. Desirable Characteristics Of An
Abrasive
• It should be irregular in shape so that it
presents a sharp edge.
• It should be harder than the surface it
abrades.
• Abrasive point should always fracture rather
than dull out so that always a sharp point or
edge is available.
• Abrasive should possess attrition resistance so
that it does not wear.

12. Factors affecting abrasion
• Hardness
• Shape
• Size
• Pressure
• Speed
• lubricants

13. Factors affecting rate of abrasion
Hardness
• Relates to durability of an abrasive
• Measure of a material’s ability to resist indentation
• Abrasive particle must be harder than the surface to be
abraded
• First ranking of hardness was published in 1820 by
Friedrich Mohs
• Knoop and Vickers hardness tests

14. Material Moh’s Brinell Knoop Material Moh’s Brinell Knoop
Talc 1 Alumnium oxide 9 1700 1900
Gypsum 2 Silicon carbide 9-10 3000 2500
Chalk 3 Boron carbide 9-10 2800
Rouge 5-6 Diamond 10 >3000 7000
Pumice 6 450 560 SUBSTRATES
Tripoli 6-7 Acrylic 2-3 25
Garnet 6.5-7 550 Pure gold 2.5-3 30
Tin oxide 6-7 Porcelain 6-7 400
Sand 7 650 800 Amalgam 4-5 90
Cuttle 7 650 800 Dentin 3-4
Tool steel 800 Enamel 5-6 270
Zirconium
7-7.5 Glass 5-6
silicate
Tungsten
carbide
9 1200 2100 Resin composite 5-7 200

15. Shape
• Sharp, irregular particle produces deeper abrasion than
rounder particle under equal applied force
• Numerous sharp edges - enhanced cutting efficiency
• Abrasion rate of an abrasive decreases with use

16. Size
• Larger particles size, abrade a surface more rapidly
• Particles based on their size:
1. Coarse -53 μm to 142 μm,
2. Medium -15 μm to 52 μm,
3. Fine - 7 to 14 μm.
4. Superfine – 2 to 6 um.

17. Pressure
Greater force during finishing
Abrasive cut deeper into the surface
More rapid removal of material
Raise in temperature within the substrate
Distortion or physical changes within the
substrate

18. • Deeper and wider scratches are produced by increasing
the applied force from F1and F2

19. Speed
Faster speed
Faster cutting rates
Temperature increases
Greater danger of overcutting

20. Lubrication
• Minimize the heat buildup
• Facilitates removal of debris
• Cooling action and removal of debris enhances
the abrasion process.
• Water is the most common lubricant
• Eg. Water, glycerin or silicone
• Excess lubrication – prevent abrasive contact

21. Abrasive Instrument Design
• Abrasive Grits.
• Bonded Abrasives.
• Coated abrasive disks and strips
• Non bonded abrasives

22. Abrasive grits
• Derived from materials that have been
crushed and passed through a series of
mesh screens
• Dental abrasive grits based on particle
size are
• Coarse
• Medium coarse
• Medium
• Fine
• Superfine

23. Bonded abrasives
• Abrasive particles are incorporated through
a binder to form grinding tool
• Particles are bonded by four general
methods:
• Sintering
• Vitreous bonding
• Resinous bonding
• Rubber bonding (latex or silicon based)

24. Type of bonding and grinding behaviour
1. Bonded abrasives that tend to disintegrate
rapidly against substrate are weak
• Increased abrasive cost - Reduced instrument
life
2. Abrasives that tend to degrade too slowly clog
with grinding debris
• Loss of abrasive efficiency, increased heat
generation, and increased finishing time

25. Maintenance of the efficiency of abrasive
• Truing : abrasive instrument is run against a
harder abrasive block until the abrasive
instrument rotates in the hand piece without
eccentricity or runout when placed on a
substrate.

26. • Dressing :
1)Reduces instrument to correct working
size, shape
2)Removes clogged debris (abrasive
blinding) - Restores grinding efficiency
Truing

27. Coated Abrasive Disks and Strips
• supplied as disks and finishing strips.
• Fabricated by securing abrasive particles to a flexible
backing material
• available in different diameters with thin and very thin
backings.
• Moisture – resistant backings are advantageous

28. Abrasive discs :
• Gross reduction, contouring, finishing, and
polishing of restoration surfaces
• Coated with aluminum oxide abrasive
Abrasive strips :
• With plastic or metal backing are available
for smoothening and polishing the
interproximal surfaces of direct and indirect
bonded restorations

29. Non bonded abrasives
• Polishing pastes - final polishing.
• Applied to substrate with a nonabrasive
device - synthetic foam , rubber, felt, or
chamois cloth.
• Dispersed in water soluble medium such as
glycerin for dental applications.
• Aluminium oxide and diamond

30. Classification :
Natural abrasives
1. Arkansas Stone
2. Chalk
3.Corundum
4.Diamond
5.Emery
6.Garnet
7. Pumice
8. Quartz
9. Sand
10. Tripoli
11. Zirconium silicate
12. Cuttle
13. Kieselguhr

31. Synthetic Abrasives
1.Silicon carbide
2.Aluminium oxide
3.Synthetic diamond
4.Rouge
5.Tin oxide

32. Arkansas stone
• Semi translucent , light gray, siliceous
sedimentary rock.
• Contains microcrystalline quartz.
• Attached to metal shanks and trued to
various shapes
• Fine grinding of tooth enamel and metal
alloys

33. Chalk
• Mineral forms of calcite.
• White abrasive composed of
calcium carbonate.
• Used as a mild abrasive paste to
polish tooth enamel, gold foil,
amalgam and plastic materials.

34. Natural Diamond
• Transparent colorless mineral
composed of carbon
• Superabrasive
• Supplied in several forms
• Bonded abrasive rotary
instruments
• Flexible metal backed abrasive
strips
• Diamond polishing pastes.
• Used on tooth structure; ceramic and
resin based composite materials

35. Diamond abrasive instruments
Introduced in the united states in 1942.
Consists of 3 parts :
metal blank
powdered diamond abrasive
metallic bonding material.
•Blank resembles a bur without blades.
•The diamonds are attached to the blank by
electroplating a layer of metal on the blank while holding
the diamonds in place against it.
•Diamond instruments are available in variety of sizes &
shapes.
•More than 200 shapes & sizes are available.
•Lack of uniform nomenclature for diamond instruments.

36. Various Shapes of Diamond abrasive instruments

37. Diamond particle factors
Particle size is categorized as:
Coarse (125-150 um)
medium (88-125 um)
Fine (60-74 um)
Very fine (38-44 um)
Diamond finishing instruments use even finer
diamonds (10-38 um)
Only cause of failure of diamond instruments is
loss of diamonds from critical areas which results
from the use of excess pressure in attempt to
increase the cutting rate.

39. Corundum
• Mineral form of aluminum
oxide
• Physical properties are inferior
to those of alpha aluminum
oxide.
• Grinding metal alloys
• A bonded abrasive in several
shapes.
• Used in instrument – White
stone

40. Emery
• Natural form of an oxide of aluminium
• Grayish- black corundum
• Coated abrasive disks
• Finishing metal alloys or acrylic resin
materials.

41. Garnet
• Dark red, very hard .
• Comprise - silicates of Al, Co,
Mg, Fe, Mn
• Garnet is coated on paper or
cloth with glue.
• Fractured during grinding 
sharp, chisel-shaped plates
• Grinding metal alloys or acrylic
resin materials.

42. Pumice
• Highly siliceous material of
volcanic origin
• Powder-crushing pumice stone
• Abrasive action is not very high
• Polishing tooth enamel, gold
foil, dental amalgam and
acrylic resins

43. Quartz
• Very hard, colorless, and
transparent.
• Crystalline particles are
pulverized to form sharp,
angular particles - coated
abrasive discs.
• Grinding tooth enamel and
finishing metal alloys.

44. Sand
• Predominantly composed of silica.
• Particles represent a mixture of color.
Making it distinct in appearance.
• Rounded to angular shape.
• Applied under air pressure to remove
refractory investment materials
• Coated on to paper disks

45. Tripoli
• Derived from light weight, friable siliceous sedimentary
rock.
• Rock is ground and made into bars with soft binders
• Color- white/grey/pink/red/yellow.
• Grey and red types
• Polishing for metal alloys and some acrylic resins.

46. Zirconium silicate / Zircon
• Off -white mineral.
• Ground to various particle sizes - coated
abrasive disks and strips.
• Component of dental prophylaxis pastes

47. Cuttle
• Referred to as cuttle fish, cuttle bone, or cuttle.
• White calcareous powder
• Available as a coated abrasive
• Polishing of metal margins and amalgam
restorations.

48. Kieselguhr
• Siliceous remains of minute aquatic plants -
diatoms.
• Coarser form - diatomaceous earth
• Excellent mild abrasive
• Risk for respiratory silicosis caused by
chronic exposure

49. Synthetic Silicon Carbide
• Extremely hard abrasive and 1st synthetic abrasive
• Highly effective cutting of metal alloys, ceramics and
acrylic resin materials.
• Abrasive in coated disks and as vitreous - bonded
and rubber instruments.

50. Aluminum oxide
• White powder
• used as bonded abrasives, coated abrasives and air
propelled abrasives.
• Finishing metal alloys, resin based composites and
ceramic materials.
• Pink and ruby variations- adding chromium compounds

51. Rouge
• Consists of iron oxide, which is the fine red
abrasive component.
• Blended in to various soft binders in to a cake
form.
• Used to polish high noble metal alloys.

52. Tin Oxide
• Extremely fine abrasive.
• Less abrasive than quartz.
• Polishing teeth and metallic
restorations in the mouth.
• Produces excellent polish of
enamel.
• Mixed with water or glycerin -
abrasive paste.

53. Synthetic Diamond
• Controllable, consistent size and shape.
• Resin bonded diamonds have sharp edges
• Larger synthetic diamond particles – greenish
• Blocks with embedded diamond particles –
truing other bonded abrasives
• Used primarily on tooth structure, ceramics
and resin based composites.

54. Dentifrices
• Available as toothpaste, gels and powders.
• The abrasive concentrations in paste and gel
dentrifices are 50% to 75% lower than those
of powder dentrifices
• Function :
• Abrasive and detergent action
• Polish teeth
• Act as vehicles

55. Prophylaxis pastes
• removal of exogenous stains, pellicle, material
alba, and oral debris.
• contain moderately abrasive materials : pumice
• Silcon dioxide and zirconium silicate are used
• Applied to teeth through rubber cup on a slow
speed handpiece

56. Precautions
• Heat generation during cutting and
contouring , finishing and polishing
procedures is a major concern.
• To avoid adverse effects to the pulp, cool
the surface using air water spray and
intermittent contact.

57. Biological hazards
• Aerosols – silica based materials (smaller
than 5μm)
• Silicosis or grinders disease
• Precautions -adequate water spray, suction
-eyeware ,facemasks
-proper ventilation

58. Recent Advances

59. Air abrasive Technology
• Alternative to rotary instrument
cutting.
• High pressure stream of 25-
30μm Al2O3.
• ‘Air polishing’- controlled
delivery of air, water and Sodium
bicarbonate slurry.

60. Uses
• Cavity preparation
• Removal of defective restorations
• Endodontic access through porcelain crowns
• Minimal preparation to repair crown margins
• Superficial removal of stains
• Roughening of internal surfaces of indirect
porcelains or composite restorations

61. CVD diamond-coated burs
• Advantages such as less noise, less pain for
the patient, precise cutting, conservative
cavity, preparation, longer lifetime, less injury
to the dental structures, no cutting of soft
tissues and easier access of the carious lesion.

62. Gripped diamond Strips
Diamond-coated stainless steel metal strips
Features:
used for smoothing, contouring, finishing and
trimming proximal, incisal and interproximal
areas
two, color-coded working areas with different
grit sizes
handles help to pull through tight contact
areas

63. Finishing and Polishing
system
designed to finish and polish all
types of resin restoratives By
incorporating a superior abrasive
into a special resin.
System uses a one-piece disc and
mandrel - with no metal boss. So
that, the possibility of discolouring
the restoration has been completely
eliminated.
It completes intermediate and final
finishing without the need to
change discs.

64. Perforated Diamond Strips
Designed for complete control during inter-proximal
reduction, shaping, and contouring.
The design assists in debris removal,
provides improved visibility, control, and
flexibility; made of stainless steel to resist
breaking and stretching.
They are color coded for grit identification:
blue for medium, red for fine and yellow for
super-fine.

65. single-gel diamond
polishing system
it can polish the surface of all
restorative materials: composite,
glass ionomer, compomer,
amalgam, precious metal and
enamel. Even porcelain achieves a
lustrous surface in less time due to
the optimal concentration of
micron-sized diamond particles.

66. SUMMARY & CONCLUSION
• Though a varied range of abrasive and
polishing agents have been described with
relation to individual dental materials, an ideal
abrasive or a polishing agent which would
satisfy all polishing needs of the dental
materials, one would say is yet to be
developed.

67. References
• Sturdevant’s Art and Science of Operative
Dentistry, 5th edition, Elsevier publications.
• Anusavice, Phillips Science of Dental
Materials, 12th edition, Elsevier publications.
• Craig . Powers and Wataha, Dental
Materials, Properties and manipulation, 8th
edition, Elsevier publications.
• Contemporary fixed prosthodontics. 2nd Edition,
Stephen F. Rosensteil.

68. Thank You